1. Field of the Invention
The present invention relates to wireless integrated circuit (IC) device components and wireless IC devices. More particularly, the present invention relates to a wireless IC device component and a wireless IC device preferably for use in a Radio Frequency Identification (RFID) system.
2. Description of the Related Art
Hitherto, RFID systems have been developed as article management systems. In such an RFID system, a reader-writer producing an induction electromagnetic-field communicates with an IC chip (also referred to as an IC tag or a wireless IC chip) in a non-contact manner. The IC chip is attached to, for example, an article or a container and stores certain information to be transmitted. The IC chip is coupled to an antenna, that is, a radiation plate to enable communication with the reader-writer.
Japanese Registered Utility Model No. 3148168 discloses a wireless IC device which includes a wireless IC, an annular electrode including a pair of ends, and a matching portion provided on the pair of ends of the annular electrode and in which a dipole radiation plate is connected to a current maximum point of the annular electrode. In the wireless IC device, the wireless IC is coupled to the matching portion and the annular electrode is electromagnetically coupled to the radiation plate. The wireless IC is coupled to the radiation plate via the annular electrode.
In the wireless IC device described above, the use of the annular electrode (coupling electrode) enables the mounting accuracy of the wireless IC to be reduced so as to improve the radiation characteristics. However, such an annular electrode (coupling electrode) has an inductive reactance complementing the impedance and there is a problem in that a long electrical length increases the value of the inductive reactance so as to deteriorate impedance matching between the wireless IC and the radiation plate.